Master of Science / Department of Computing and Information Sciences / Daniel A. Andresen / Recently, the world has been trending toward the use of Smartphone. Today, almost each and every individual is using Smartphone for various purposes benefited by the availability of large number of applications. The memory on the SD (Secure Digital) memory card is going to be a constraint for the usage of the Smartphone for the user. Memory is used for storing large amounts of data, which include various files and important document. Besides having many applications to fill the free space, we hardly have an application that manages the free memory according to the user’s choice. In order to manage the free space on the SD card, we need an application to be developed. All the important files stored on the Android device cannot be retrieved if we lose the Android device. Targeting the problem of handling the memory issues, we developed an application that can be used to provide the security to the important documents and also store unnecessary files on the distributed file servers and retrieve them back on request.

Ransomware is a type of malware that hijack victims’ computers, by encrypting or locking corresponding files, and demanding the payment of some ransom in cryptocurrency for the restoration of the files. The last few years have witnessed a sudden rise in ransomware attack incidents, causing significant amount of financial loss to individuals, institutions, and businesses. In reaction to that, ransomware detection has become an important topic for research in recent years. Currently, there are three types of ransomware detection techniques available in the wild: static, dynamic and hybrid. Unfortunately, the current static detection techniques can be easily evaded by code-obfuscation and encryption techniques. Furthermore, current dynamic and hybrid techniques face difficulties to detect novel ransomware. In the current thesis, we present an upgraded dynamic ransomware detection model with two new sets of features: grouped registry key operation, and combined file entropy and file signature. We analyze the new feature model by exploring and comparing 3 different linear machine learning techniques: SVM, Logistic Regression and Random Forest. The proposed approach help achieves improved detection accuracy and provides the ability to detect novel ransomware. Furthermore, the proposed approach helps differentiate user-triggered encryption from ransomware-triggered encryption, which allows saving as many files as possible during an attack. To conduct our study, we use a new public ransomware detection dataset collected at the ISOT lab, which consists of 666 ransomware and 103 benign binaries. Our experimental results show that our proposed approach achieves relatively high accuracy in detecting both previously seen and novel ransomware samples. / Graduate

A limpeza e modelagem dos canais radiculares consiste em uma etapa fundamental para o sucesso da terapia endodôntica. O objetivo deste estudo foi avaliar um novo conceito de instrumento endodôntico Self Adjusting File (SAF), e instrumentos rotatórios de NiTi, na capacidade de limpeza de canais achatados por meio de microscopia óptica. Vinte e dois incisivos inferiores instrumentados com instrumentos rotatórios K3 (n=11) e sistema SAF (n=11), tiveram seus terços apicais submetidos ao processamento histológico e analisados em microscopia óptica (40×). As imagens capturadas pelo software Adobe Photoshop 5.1 foram analisadas com auxilio de grade de integração do software Image J. O perímetro de ação dos instrumentos nas paredes dos canais radiculares foi determinado com auxilio do software Image J e uma mesa digital Bamboo. Os dados obtidos foram submetidos à análise de variância e teste de T não pareado corrigido pelo teste de Welch, considerando-se a presença de debris no terço apical e a superfície de dentina sem contato com o instrumento (&alpha;=5%). A análise estatística mostrou haver diferença significante entre os grupos. Canais instrumentados com o sistema endodôntico SAF apresentaram valores percentual de debris e superfície não tocada pelo instrumento menores (2,18 ± 2,71 e 12,33 ± 7,85 respectivamente) quando comparado com canais instrumentados com instrumentos rotatórios (13,11 ± 12,98 e 53,54 ± 15,95, respectivamente) (p<0.05). Concluiu-se que o sistema SAF proporcionou melhor preparo de canais radiculares por tocar mais nas paredes radiculares promovendo consequentemente melhor limpeza. / Cleaning and shaping of root canals are essential steps for the success of endodontic therapy. The purpose of this study was to evaluate a new concept of endodontic instrument - the Self Adjusting File (SAF) system - and NiTi rotary instruments, regarding their cleaning capacity in flattened root canals, using optical microscopy. Twenty-two mandibular incisors prepared with K3 rotary instruments (n=11) and SAF system (n=11) had their apical thirds subjected to histological processing and analyzed by optical microscopy (40×). The images captured by Adobe Photoshop 5.1 software were analyzed with the integration grid of Image J software. The perimeter of action of the instruments on the root canals walls was determined using Image J software and a Bamboo digital tablet. Data were analyzed statistically using analysis of variance and unpaired t-test with Welchs correction, considering the presence of debris in the apical third and the root dentin surface untouched by the instrument (&alpha;=5%). The statistical analysis revealed significant difference between the groups. Canals prepared with the SAF system presented lower percent values of debris and untouched root dentin surfaces (2.18 ± 2.71 and 12.33 ± 7.85, respectively) compared with canals prepared with rotary instruments (13.11 ± 12.98 and 53.54 ± 15.95, respectively) (p<0.05). In conclusion, the SAF system was associated with better root canal preparation, as it touched more the root dentin walls and consequently promoted a more effective cleaning.

Typescript (photocopy). / Digitized by Kansas Correctional Industries / Department: Computer Science.

A limpeza e modelagem dos canais radiculares consiste em uma etapa fundamental para o sucesso da terapia endodôntica. O objetivo deste estudo foi avaliar um novo conceito de instrumento endodôntico Self Adjusting File (SAF), e instrumentos rotatórios de NiTi, na capacidade de limpeza de canais achatados por meio de microscopia óptica. Vinte e dois incisivos inferiores instrumentados com instrumentos rotatórios K3 (n=11) e sistema SAF (n=11), tiveram seus terços apicais submetidos ao processamento histológico e analisados em microscopia óptica (40×). As imagens capturadas pelo software Adobe Photoshop 5.1 foram analisadas com auxilio de grade de integração do software Image J. O perímetro de ação dos instrumentos nas paredes dos canais radiculares foi determinado com auxilio do software Image J e uma mesa digital Bamboo. Os dados obtidos foram submetidos à análise de variância e teste de T não pareado corrigido pelo teste de Welch, considerando-se a presença de debris no terço apical e a superfície de dentina sem contato com o instrumento (&alpha;=5%). A análise estatística mostrou haver diferença significante entre os grupos. Canais instrumentados com o sistema endodôntico SAF apresentaram valores percentual de debris e superfície não tocada pelo instrumento menores (2,18 ± 2,71 e 12,33 ± 7,85 respectivamente) quando comparado com canais instrumentados com instrumentos rotatórios (13,11 ± 12,98 e 53,54 ± 15,95, respectivamente) (p<0.05). Concluiu-se que o sistema SAF proporcionou melhor preparo de canais radiculares por tocar mais nas paredes radiculares promovendo consequentemente melhor limpeza. / Cleaning and shaping of root canals are essential steps for the success of endodontic therapy. The purpose of this study was to evaluate a new concept of endodontic instrument - the Self Adjusting File (SAF) system - and NiTi rotary instruments, regarding their cleaning capacity in flattened root canals, using optical microscopy. Twenty-two mandibular incisors prepared with K3 rotary instruments (n=11) and SAF system (n=11) had their apical thirds subjected to histological processing and analyzed by optical microscopy (40×). The images captured by Adobe Photoshop 5.1 software were analyzed with the integration grid of Image J software. The perimeter of action of the instruments on the root canals walls was determined using Image J software and a Bamboo digital tablet. Data were analyzed statistically using analysis of variance and unpaired t-test with Welchs correction, considering the presence of debris in the apical third and the root dentin surface untouched by the instrument (&alpha;=5%). The statistical analysis revealed significant difference between the groups. Canals prepared with the SAF system presented lower percent values of debris and untouched root dentin surfaces (2.18 ± 2.71 and 12.33 ± 7.85, respectively) compared with canals prepared with rotary instruments (13.11 ± 12.98 and 53.54 ± 15.95, respectively) (p<0.05). In conclusion, the SAF system was associated with better root canal preparation, as it touched more the root dentin walls and consequently promoted a more effective cleaning.

Root canal preparation in narrow, curved canals is a challenge even for experienced endodontists. Recently nickel-titanium (NiTi) hand files have played an important role in root canal preparation, particularly in curved root canals. Nickel-titanium endodontic instruments were first investigated in 1988 by Walia et al. who found that NiTi files have two to three times more elastic flexibility in bending and torsion, as well as superior resistance to torsional fracture compared with similar stainless steel files.

Root canal preparation in narrow, curved canals is a challenge even for experienced endodontists. Recently nickel-titanium (NiTi) hand files have played an important role in root canal preparation, particularly in curved root canals. Nickel-titanium endodontic instruments were first investigated in 1988 by Walia et al. who found that NiTi files have two to three times more elastic flexibility in bending and torsion, as well as superior resistance to torsional fracture compared with similar stainless steel files.

P2P Grid computing seeks the convergence of Grid and P2P technologies. Deploying a P2P Grid middleware on a set of computers enables an organization to automatically barter computing time with other Internet-connected organizations. Such P2P exchanges of computing time enable individual Peers, i.e. organizations, to transparently aggregate large amounts of computational power with minimal infrastructure requirements or administrative cost. Challenges arise from the requirement for scalability and robustness. Individual worker nodes are unreliable, as P2P Grids operate on unmanaged desktop computers. A specificity of P2P Grids is that each Peer can reclaim at any time the computational power of worker nodes supplied to other Peers, leading to bursts of execution preemption. These are the major contributions of our dissertation: * Firstly, we propose a new P2P Grid architecture, the Lightweight Bartering Grid (LBG). Through systematic cooperation between Grid nodes, the reliability of execution of computational requests is greater than the sum of the reliabilities of worker nodes. * Secondly, we propose a highly scalable data transfer architecture. It is based both on the BitTorrent P2P file sharing protocol and on the removal of the temporal cost of downloading redundant copies of input data files. * Thirdly, besides a middleware implementation of LBG, we also provide an implementation of a discrete-event simulator. Its originality resides in the weaving of the simulator code into the bartering code of the middleware, which is made possible through the virtualization of Grid nodes. This enables reproducible testing and accurate performance evaluation of the bartering policies because the Peers of a simulated Grid make the same bartering decisions as Peers deployed on real computers. The LBG architecture exhibits the following remarkable features: * The scheduling model supports the queueing of external requests and the architecture enables a flexible study of bartering policies. * The architecture is open, flexible, lightweight and facilitates software engineering. It enables the easy development, testing, evaluation and deployment of combinations of scheduling policies. * The architecture is fully P2P.

Cloud computing is pervasive in our daily life. For instance, I usually use Google¡¦s GMail to receive e-mail, Google Document to edit documents online and Google Calendar to make my daily schedule. We can say that Google provides a ¡§Platform as a Service (PaaS)¡¨, which delivers a computing platform as a service, and the platform sustaining lots of cloud applications such as I mentioned above. However, the cloud computing platform of Google is private: we cannot trace its source code and make cloud applications on it! Fortunately, there¡¦s an open source project supported by Apache named ¡§Hadoop¡¨, which has a distributed file system which is very like Google File System (GFS) called ¡§Hadoop distributed file system (HDFS)¡¨. In order to observe the properties of HDFS, we design and implement a HDFS-based FTP server system called FTP-ON-HDFS system, say, a FTP server whose storage is HDFS. There are a web-console for FTP administrator, a FreeRADIUS server and a MySQL database for user authentication, a NameNode daemon on its machine, a SecondaryNameNode on its machine and five DataNode daemons and on five different machines in FTP-ON-HDFS system. Our FTP-ON-HDFS system can tune two QoS parameters: ¡§data block size¡¨ and ¡§data replication¡¨. Then, we tuned ¡§data block size¡¨ and ¡§data replication¡¨ in our system and compared its performance with Hadoop File System (FS) shell command and normal vsftpd. On the other hand, FUSE can mount HDFS from remote cluster to local machine, and make use of the permission of the local machine to manage HDFS. So, we compared the performance of FUSE with HDFS (FUSE-DFS) and our FTP-ON-HDFS system.

A system is developed which facilitates communication between a Personal Computer and a Mainframe, and can do both directions, and lets the user execute Unix shell commands while the file transfer is in process. This communication system consists of two programs, one named "Thesis.EXE" that runs on a DOS based machine, and one named named "COMMGREEK" that runs on a Unix based machine. / Department of Computer Science